JPH03183023A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To form the film of gamma-Fe2O3 having less defects by magnetron sputtering on a substrate by disposing a magnetic pole of a prescribed structure opposite to the rear of a target essentially consisting of Fe in a vacuum chamber and filling an inert gas contg. O2 in the chamber. CONSTITUTION:The inert gas contg. O2 is maintained under 4X10<-4> to 2X10<-3> Torr in the vacuum chamber. The rear of the target 10 essentially consisting of the Fe is disposed with an inner peripheral annular magnet 4 magnetized in parallel with the target surface on the inner side of the outer peripheral annular magnetic pole 3 magnetic coupled by a yoke 5 in such a manner that the magnetic pole 3 side is of the same pole as the magnetic pole 3. The central magnet 2 is made into the polarity reverse from the polarity of the outer peripheral annular magnetic pole 3. The magnetic thin film essentially consisting of the gamma-Fe2O3 is formed on a rigid substrate by the magnetron sputtering. The max. value of the magnetic flux density component parallel with the target surface is maintained at 200 to 400G to expand the discharge generation region and to increase the efficiency of utilizing the target. Further, the durability of the magnetic layer and less defects are compatibly obtd. when the electric power density PD per 1 piece of the target and the O2 flow rate are selected at a prescribed relation.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a magnetic recording medium, and in particular, to
The present invention relates to a method of manufacturing a magnetic recording medium having a continuous thin film type magnetic layer containing Fezes as a main component.

<Prior Art> A hard type magnetic disk in which a magnetic layer is formed on a rigid substrate and a floating magnetic head are used in magnetic disk drives used in computers and the like.

Conventionally, coated magnetic disks have been used in such magnetic disk drive devices, but as the capacity of magnetic disks has increased, sputtering methods have been used because they are advantageous in terms of magnetic properties, recording density, etc. 2. Description of the Related Art Thin-film magnetic disks having a continuous thin-film magnetic layer formed by a vapor deposition method or the like have come into use.

Thin-film magnetic disks are made by plating an N1-P underlayer on an AI2-based disk-shaped metal plate, or by oxidizing the surface of this metal plate to form alumite. It is generally constructed by sequentially depositing a Cr layer, a metal magnetic layer such as Go-Ni, and a protective lubricant film such as C by sputtering.

However, metal magnetic layers such as Go-Ni have low corrosion resistance and low hardness, causing problems in reliability. On the other hand, Japanese Patent Application Laid-Open Nos. 62-43819 and 63-17521
The magnetic thin film mainly composed of iron oxide as described in Japanese Patent No. 9 is chemically stable, so there is no fear of corrosion, and it also has sufficient hardness.

<Problem to be solved by the invention> A magnetic layer mainly composed of iron oxide is usually made of y-FetOs.
Alternatively, Co-containing T-Fe20. It consists of

The γ-Fe2rs magnetic layer is usually formed by a direct method or an indirect method.

As direct methods, direct neutralization methods, direct reduction methods, and direct oxidation methods are usually used.

The direct neutralization method uses Fe3O4 in an Ar gas atmosphere.
This method forms a Fe5O4 film using a target and oxidizes it to obtain a γ-Fezes film.

The direct reduction method uses an α-Fe2rg target in an Ar gas atmosphere containing H2 gas to reduce Fe3O<
This method forms a film and oxidizes it to obtain a γ-Fears film.

In the direct oxidation method, reactive sputtering is performed using an Fe target in an Ar gas atmosphere containing 0□ gas to form a Fe3O4 film, which is then oxidized to form γ-Fears.
This is a method for obtaining membranes.

In addition, in the indirect method, an α-Fe2rs film is formed by reactive sputtering using an Fe target in an Ar gas atmosphere containing 02 gas, and this is reduced to form an Fe2rs film.
In this method, a 3O4 film is formed and further oxidized to obtain a γ-Fears film.

In any of these methods, magnetron sputtering is usually used because a high sputtering rate can be obtained.

FIG. 3 is a sectional view showing the configuration of the main parts of the magnetron sputtering device.

As shown in FIG. 3, in the magnetron sputtering method, a target 10 is provided in a vacuum chamber (not shown) into which an inert gas is introduced, and a magnetic field generating means 101 is placed on the back side of the target 10.

The magnetic field generating means 101 usually includes a central magnet 102 and an annular magnet 103 arranged to surround the central magnet 102, which are magnetically coupled by a yoke 105.

The target 10 is usually used as the cathode, and the wall of the vacuum chamber is often used as the anode, but it may also be provided independently.

In such a configuration, magnetic flux leaking from the target 10 causes magnetron discharge in the vicinity of the surface of the target 10 in which the electric field and the magnetic field are perpendicular to each other. As a result, the electrons move in a continuous trajectory near the surface of the target 10, increasing the ion density and increasing the number of ions that collide with the target 10. (not shown) also increases.

Generally, in sputtering, the target is eroded as sputtering progresses, but in magnetron sputtering, the target is locally eroded as shown in FIG.

The eroded region at this time corresponds to a region where the direction of the leakage magnetic flux is approximately parallel to the target surface, but in conventional magnetron sputtering, this region is narrow and the efficiency of using expensive target material is low.

Moreover, when reactive sputtering is performed in an atmosphere containing O2 gas, as in the formation of the γ-pezosMi layer described above, a more serious problem arises.

For example, when forming a Fe3O4 film using the above-mentioned direct oxidation method when forming a γ-Fears magnetic layer, areas other than the eroded portions of the target surface may be oxidized and changed, or sputtered particles may re-deposit. As a result, a blackened surface deterioration layer is formed.

As the sputtering is repeated, the depth of the eroded area increases and the area of the eroded area also increases, and this blackened area is also sputtered, and the blackened area becomes lumpy and the bullets come out. Foreign matter ejected from the bullets may enter or adhere to the Fear4 film deposited on the substrate, or these deposits may peel off from the surface of the Fe5Oa film after sputtering, resulting in film defects in these portions.

However, since digital recording is mainly performed on the magnetic layer of the above-mentioned thin-film magnetic disk, extremely low film defects are required.

The present invention has been made under these circumstances, and an object of the present invention is to provide a method for manufacturing a magnetic recording medium having a continuous thin film type magnetic layer with few film defects.

Means for Solving the Problems> Such objects are achieved by the present invention as described in (1) to (5) below.

(1) In the step of forming a magnetic layer mainly composed of γ-Fezes on a rigid substrate, a target mainly composed of Fe is placed in a vacuum chamber, a substrate is placed on the surface side of the target, and the target An outer annular magnetic pole is disposed facing the back surface, and an inner annular magnet magnetized in a direction substantially parallel to the target surface is placed inside the outer annular magnetic pole, and the outer annular magnetic pole side has the same polarity as the outer annular magnetic pole. A method for manufacturing a magnetic recording medium, characterized in that the vacuum chamber is filled with an inert gas containing 02 gas and magnetron sputtering is performed to form a sputtered film on the substrate.

(2) The method for manufacturing a magnetic recording medium according to (1) above, wherein magnetron sputtering is performed by arranging a central magnetic pole of opposite polarity to the outer annular magnetic pole inside the inner annular magnet.

<3) The maximum value of the magnetic flux density component in the direction parallel to the target surface on the target surface is set to 200 to 400.
The method for manufacturing a magnetic recording medium according to (1) or (2) above, wherein magnetron sputtering is performed while maintaining the G range.

(4) The inside of the vacuum chamber was heated to 4, OX 10-'Torr.
~2. The method for manufacturing a magnetic recording medium according to any one of (1) to (3) above, wherein magnetron sputtering is performed while maintaining the pressure at Ox 10-'' Torr.

(5) Power density P per target
D (Watt/cm2) and 02 gas flow rate OGF (SC
CM), OGF = (3,7 ± 0.8) PD (3,9 ± 0.7) and OGF > 0. ) The method for manufacturing a magnetic recording medium according to any one of the above.

Effect> In the present invention, reactive magnetron sputtering is performed in an atmosphere containing 02 when forming the γ-FetOs magnetic layer. In this reactive magnetron sputtering, a magnetron sputtering apparatus having a magnetic field generating means composed of the above-mentioned outer circumferential annular magnetic pole and inner circumferential annular magnetic pole, preferably a central magnetic pole in addition to these, is used to reduce the leakage magnetic flux density from the target. Maintain within the above range.

For example, when forming a γ-Fears magnetic film by the direct oxidation method, an Fe5O4 film is formed using an Fe target in an Ar gas atmosphere containing 02 gas. A black foreign material layer is formed on the target surface, and as sputtering progresses, this foreign material is thrown out and mixed into or adheres to the sputtered film on the substrate surface, causing film defects.

However, if the magnetic field generating means described above is used, the proportion of the component parallel to the target surface of the leakage magnetic flux density from the target surface can be increased, so that the erosion area of the target is expanded. In this way, in the present invention, since the erosion region is wide from the start of sputtering, the formation of a black particle layer on the surface of the Fe target is prevented, the incorporation of foreign substances into the Fe5O4 film is reduced, and the final result is a γ film with extremely few film defects. -Fe2
An rs magnetic layer is obtained.

Therefore, in the magnetic recording medium obtained by the present invention, errors caused by defects in the magnetic layer are significantly reduced, and therefore the present invention is extremely suitable for manufacturing a magnetic recording medium for recording digital signals.

In addition, the leakage magnetic flux density from the target is 200 to 400.
In the case of G, such an effect is further improved.

Furthermore, in the present invention, the pressure during sputtering is set to 4.
OX 10-'Torr~2. OX 10-”To
When maintained at rr, the effects of the present invention are further improved.

When the sputtering pressure is reduced in this way, the plasma expands, and in addition to the effect of the magnetic field generating means described above, the erosion area on the target surface further expands. As a result, contamination of foreign matter into the Fear 4 film is significantly reduced.

Specific composition> Hereinafter, a specific configuration of the present invention will be explained in detail.

The present invention is applied to forming a continuous thin film type magnetic layer containing γ-Fears as a main component on a rigid substrate.

1 and 2 show a preferred example of the configuration of the main parts of the magnetron sputtering apparatus used in the present invention.

In the illustrated configuration, a target 10 is placed in a vacuum chamber (not shown) into which an atmospheric gas such as an inert gas or a reactive gas is introduced.
A magnetic field generating means 1 is arranged on the back side of the target 10, and a substrate (not shown) is arranged facing the surface of the target 10. The target 10 is used as a cathode, and an anode is provided, or the substrate or a vacuum chamber is used as an anode.

In such magnetron sputtering equipment, when an electric field is applied between the cathode and anode, a magnetron discharge is generated near the target surface where the electric field and magnetic field are orthogonal, and electrons move in a continuous trajectory near the target surface. do.

The inert gas is turned into plasma by the electrons, and the generated ions collide with the target surface to perform sputtering, and atoms ejected from the target are deposited on the substrate surface to form a sputtered film.

In the present invention, the target 10 is made of F such as Fe or Fe alloy.
A magnetic metal whose main component is e is used.

The magnetic field generating means 1 usually includes a central magnet 2 and an outer annular magnet 3.
and an inner circumferential annular magnet 4, these magnets being magnetically coupled by a yoke 5.

The central magnet 2 is magnetized in a direction substantially perpendicular to the surface of the target 10, and has a central magnetic pole 21 facing the back surface of the target 10.

The outer circumferential annular magnet 3 is arranged so as to surround the central magnet 2, and has an outer circumferential annular magnetic pole 31 facing the back surface of the target 10.

The central magnetic pole 21 and the outer annular magnetic pole 31 have opposite polarities.

The inner circumferential annular magnet 4 is arranged between the central magnet 2 and the outer circumferential annular magnet 3, and is magnetized in the radial direction.

The inner circumferential annular magnet 4 is arranged so that the center magnetic pole 21 side has the same polarity as the center magnetic pole 21 .

Such a magnetic field generating means 1 is obtained by adding an inner ring-shaped magnet to the magnetic field generating means in a conventional magnetron sputtering apparatus as shown in FIG.

In the present invention, since the target IO is a magnetic material, a portion of the magnetic flux from the magnetic field generating means is captured within the target, and magnetron discharge occurs only in the region where the target is magnetically saturated and the magnetic flux leaks. Therefore, in order to expand the eroded area of the target surface, it is necessary to cause magnetic flux leakage over a wide range of the target surface.

In order to effectively expand the area where magnetic flux leaks when a magnetic target is used, it is preferable that the inner circumferential annular magnet has the configuration shown in FIG. 1.

In the example shown in FIG. 1, the inner circumferential annular magnet 4 includes a first inner circumferential annular magnet 41 provided in contact with the outer circumferential annular magnet 3, and a second inner circumferential annular magnet 42 provided in contact with the central magnet 2. It consists of

The outer circumferential annular magnetic pole 31 works as an extremely strong magnetic pole by contacting the first inner circumferential annular magnet 41 with the same polarity. The magnetic pole on the center magnetic pole 21 side of the first inner circumferential annular magnet 41 attracts the leakage magnetic flux on the target surface and increases the component of the leakage magnetic flux parallel to the target surface.

On the other hand, the central magnetic pole 21 works as an extremely strong magnetic pole by contacting the second inner circumferential annular magnet 42 with the same polarity.

The magnetic pole of the second inner circumferential annular magnet 42 on the outer circumferential annular magnetic pole 31 side attracts the leakage magnetic flux on the target surface and increases the component of the leakage magnetic flux parallel to the target surface.

Due to such an effect, the magnetic field generating means l can leak sufficient magnetic flux from the magnetic target whose main component is Fe, and furthermore, it is possible to make the proportion of the component parallel to the target surface of this leaked magnetic flux extremely high. I can do it.

In the present invention, the embodiment is not limited to the embodiment shown in FIG. 1, but the inner circumferential annular magnet 4 may be composed of one annular magnet as shown in FIG. 2.

The inner circumferential annular magnet 4 with this configuration directs leakage magnetic flux to the target 1.
0 surface, and has the effect of increasing the proportion of the component of leakage magnetic flux parallel to the target surface.

Although the arrows in Figures 1 and 2 indicate the direction of magnetization, the directions of magnetization of the central magnet, outer ring magnet, and inner ring magnet may be opposite to those shown in the figures. Of course.

The magnetic field generating means shown in Figures 1 and 2 was described in Paper N of the 10th International Conference on Rare Earth Magnets (Kyoto, May 17-19, 1989, sponsored by the Unexplored Science and Technology Association).
o, 19AO402.

Further, the present invention is not limited to these examples, and any configuration may be used as long as the inner circumferential annular magnet is arranged so as to increase the component of leakage magnetic flux parallel to the target surface.

That is, if the magnetic field generating means has the outer circumferential annular magnetic pole 31 and the inner circumferential annular magnet 4 as described above, the central magnetic pole 2
1 does not necessarily need to be provided.

Further, the inner circumferential annular magnet may be composed of three or more annular magnets.

Furthermore, the central magnet, the outer circumferential annular magnet, and the inner circumferential annular magnet may each be composed of a plurality of magnet pieces.

Furthermore, instead of using the yoke 5, a stationary magnet having a central magnetic pole and an outer annular magnetic pole having the above relationship may be used.

Note that the outer circumferential annular magnetic pole does not need to be annular, and its outer edge shape may be of various shapes such as a rectangle.

In the present invention, when performing sputtering using a magnetron sputtering apparatus having the above-described magnetic field generating means, the leakage magnetic flux density from the target surface is preferably set to 200 to 4
00G, more preferably 200 to 300G.

Here, the leakage magnetic flux density is the maximum value of the component of the leakage magnetic flux density in a direction parallel to the target surface, and is a value measured on the target surface.

Note that repeated sputtering erodes the target and creates recesses on the surface, but in such a case, the magnetic flux density is measured on the surface of the recesses.

Further, the magnetic flux density can be measured using a Gaussmeter using a Hall element or the like.

By setting the leakage magnetic flux density within this range, the proportion of magnetic flux in a direction substantially parallel to the target surface increases, and the region where magnetron discharge occurs is expanded.

When the leakage magnetic flux density is below this range, magnetron discharge is difficult to occur, and when it exceeds this range, the eroded area of the target is critically reduced.

The intensity of the leakage magnetic field during sputtering is preferably constant, but may vary within the above range.

In addition, the leakage magnetic flux density changes as the target is eroded by repeated sputtering, but in this case, in order to keep the leakage magnetic flux density within the above range, the power applied to the target, the usage time, etc. are monitored and the back surface of the target is It is preferable to adopt a configuration in which the magnetic field strength at the position can be changed.

In order to change the magnetic flux density on the back surface of the target, it is preferable to use an electromagnet as the magnet because it is easy to control, but there is also a configuration in which a permanent magnet is used as the magnet and the distance between the magnet and the target is controlled. You can also use it as

In the present invention, the leakage magnetic flux density is set to the above range, and the gas pressure in the vacuum chamber, that is, the sputtering pressure is set to 4. O
X 10-'Torr ~2. OXl 0-”Tor
It is preferable to set it to r.

When the sputtering pressure is reduced in this manner, in addition to the effect of the low leakage magnetic field strength described above, the erosion area on the target surface is further expanded, and the contamination of foreign matter into the Fe3O4 film is significantly reduced.

When the sputtering pressure is less than this range, magnetron discharge is difficult to occur, and when it exceeds this range, further expansion of the eroded region cannot be expected.

The magnetron sputtering method carried out under the above conditions is used to form a continuous thin film type magnetic layer containing γ-Fetus as a main component.

The continuous thin film type magnetic tank whose main component is γ-Fears is
Formed by direct or indirect methods.

The direct method is a method in which a Fe5O4 film is first formed and then oxidized to obtain a γ-FeaO3 film.

As a method for forming a Fe3O4 film using the direct method,
As mentioned above, the direct oxidation method is carried out in an Ar gas atmosphere containing 02 gas using a target mainly composed of Fe, the direct reduction method is carried out in a reducing atmosphere using α-Fe20i as a target, and the direct reduction method is carried out in a reducing atmosphere using α-Fe20i as a target. A direct neutralization method using Fe3O< is mentioned.

Among these methods, the direct oxidation method is most likely to cause foreign matter to be mixed into or attached to the sputtered film, so the present invention is applied to the direct oxidation method.

Further, the direct oxidation method is preferable because sputtering can be easily controlled and the film formation rate is high.

In the present invention, when forming a Fezes film using a direct oxidation method, the magnetic field generating means described above is used, preferably the range of leakage magnetic flux density from the target surface is maintained within the range described above,
More preferably, the sputtering pressure (total pressure of Ar gas and 02 gas) is within the above range.

By performing reactive magnetron sputtering under such conditions, the formation of a black variant layer on the target surface can be suppressed, and a magnetic layer with extremely few defects can be obtained.

Note that in order to improve the durability of the magnetic layer, the power density per target P D (Watt/c
m2) and 02 gas flow rate OGF (SCCM), OGF= (3,7±0.8) PD(3,9±
0.7) and OGF>0.

By performing reactive sputtering under such conditions, the durability of the magnetic layer, especially the C8S durability, becomes extremely high.

02 When the gas flow rate and power density are in such a relationship, a black denatured layer is likely to occur on the target surface, and as a result, defects in the magnetic layer are likely to occur, but by applying the present invention, high durability and fewer It becomes possible to achieve both defects and defects.

In the present invention, it is preferable that the 0□ gas be introduced near the substrate.

For details of Fear4 thin film formation by direct method, see Journal of the Institute of Electronics and Communication Engineers '80/9 Vol. J63'-CNQ, 9
p, 609-616, and in the present invention, it is preferable to form the magnetic layer according to this.

Note that in the present invention, it is preferable to use a high frequency magnetron sputtering method.

Fe3O4 deposited by sputtering is γ-Fea
Oxidized to r3.

This oxidation takes place at a gas partial pressure of O, OS ~ 0.8 atm,
The heat treatment may be carried out in an atmosphere with a total pressure of about 0.5 to 2 atmospheres, and it is usually preferable to carry out the heat treatment in the atmosphere.

The holding temperature during heat treatment is 200 to 400°C, especially 23°C.
It is preferable that the temperature is 0 to 330°C, and the temperature holding time is
The time period is preferably 10 minutes to 10 hours, particularly 1 hour to 5 hours.

Note that it is preferable that α-FezOa is contained in the magnetic layer containing γ-Fe2rs as a main component in order to improve durability. In order to keep the content of α-Fezes at an effective level for improving durability, the temperature increase rate should be 3.5 to 20'C/min, especially 5.0 to 12°C during the above heat treatment.
/ min is preferable.

Note that the temperature increase rate may be constant, gradually increased or decreased, or a plurality of temperature increase rates may be combined to increase the temperature to the holding temperature.

Co, Ti, Cu, etc. may be added to the magnetic layer as necessary, and Ar, etc. contained in the film forming atmosphere may be contained.

Co is an effective element for adjusting coercive force. The content of Co in the magnetic layer is preferably such that it replaces Fe by 10 wt% or less. Further, in order to make the magnetic layer contain Co, a Fe target containing Co may be used.

The thickness of the magnetic layer is determined by considering productivity, magnetic properties, etc.
It is preferable to set the number to about 0 to 3000 people.

In the indirect method, an α-Fetrs film is formed by reactive sputtering using a target containing Fe as a main component in an Ar gas atmosphere containing 02 gas, and this is reduced to form an Fe3O+ film. After further oxidation, γ
- This is a method for obtaining a Fe2es film. In this indirect method,
Similar to the direct oxidation method described above, the present invention is extremely effective because it includes a step of sputtering a target containing Fe as a main component in an oxidizing atmosphere, and the amount of 02 gas in the atmosphere is large.

For a rigid substrate on which a magnetic layer is formed on the surface, the manufacturing process is simplified as there is no need to provide an underlayer, and it is also easy to polish and control the surface roughness. It is preferable to use glass because it can withstand heat treatment during the formation of the magnetic layer and to control its surface roughness.

As the glass, it is preferable to use tempered glass, particularly surface-strengthened glass obtained by chemical strengthening.

Furthermore, a lubricating film containing an organic compound, an inorganic protective film, or the like may be provided on the magnetic layer.

<Example> Hereinafter, the present invention will be explained in further detail by giving specific examples of the present invention.

[Formation of Feao4 film] An aluminosilicate glass substrate with an outer diameter of 130 mm, an inner diameter of 40 mm, and a thickness of 1.9 mm was polished and further subjected to chemical strengthening treatment. The chemical strengthening treatment was performed by immersing the sample in molten potassium nitrate at 43O<0>C for 10 hours.

Next, the surface of this glass substrate was smoothed by mechanochemical polishing. A polishing liquid containing colloidal silica was used for mechanochemical polishing.

The surface roughness Rmax of the glass substrate after polishing was 30.

A magnetic layer containing γ-Fear3 as a main component was formed on the surface of the cleaned glass substrate by a direct oxidation method.

First, preliminary sputtering was performed in an Ar gas atmosphere to remove the oxide film on the target surface. Note that a 1 wt% Go-Fe alloy was used as the target.

Next, reactive sputtering is performed by introducing Ot gas,
A Fe3O3 film was formed. Note that 02 gas was introduced near the substrate.

For this reactive sputtering, a magnetron sputtering apparatus having the configuration shown in FIG. 1 or 2 was used, and various Fe3O< films were formed by changing the sputtering conditions.

For comparison, F
An e3O4 film was formed.

The thickness of these Fe3O+ films was 2000.

Note that the thickness of the target was 3 mm.

The leakage magnetic flux density of the target surface during sputtering (the maximum value of the component of the magnetic flux density measured on the target surface in the direction parallel to the target surface), the applied power density PD, and 0.00% per target. The gas flow rate OGF is shown in Table 1.

Although the leakage magnetic flux density changes due to erosion of the target surface as sputtering progresses, the leakage magnetic flux density was kept constant by adjusting the distance between the target and the magnetic field generating means.

The surface of each Fe5O4 film formed in this way was examined at a magnification of 3
The film was observed using an optical microscope with a magnification of 0 times, and the number of foreign particles present within a 1 cm x 1 cm area was measured at four arbitrary locations on the film surface, and the total was calculated. The results are shown in Table 1.

Note that Table 1 also includes the drawing numbers in which the magnetic field generating means used are described.

[Shape of γ-Fe*Os magnetic layerffl] Each Fe3O4 film shown in Table 1 below was heated in air for 310°C.
The mixture was oxidized at .degree. C. for 1 hour to form a .gamma.-Fears magnetic layer, and a magnetic disk was obtained.

For these magnetic disks, use the following magnetic head,
C8S durability was evaluated based on the following criteria.

Aflz with Vickers hardness of 2200 kgf/mm2
After forming a thin film magnetic head element on a 03-TiC substrate, it was processed into a magnetic head shape and attached to a support spring (gimbal) to produce an air bearing type floating magnetic head. Rmax of the magnetic head flying surface was set to 130A.

The flying height can be adjusted to 0 or 1 by adjusting the slider width and gimbal load.
-.

A C8S test was conducted at 25° C. and a relative humidity of 30% using a vertical magnetic head.

C8S was performed by repeating the cycle shown in FIG. 4, and the number of times until the recording/reproducing output became less than half of the initial level was measured, and the following 5-level evaluation was performed.

Q: 100,000 times or more ○: 50,000 times or more and less than 10,000 times Δ: 20,000 times or more and less than 50,000 times ×: 10,000 times or more and less than 20,000 times × ×: less than 10,000 times When a reproduction test was carried out, it was confirmed that there was a lack of reproduction output corresponding to the above-mentioned film defect.

From the results of the above examples, the effects of the present invention are clear.

<Effects of the Invention> According to the present invention, a magnetic recording medium having a continuous thin film type magnetic layer with few film defects and high durability is realized.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing the magnetic field generating means and target of the magnetron sputtering apparatus used in the present invention. FIG. 3 is a sectional view showing a magnetic field generating means and a target of a conventional magnetron sputtering apparatus. FIG. 4 is a graph showing one cycle of C8S. Explanation of symbols 1.101...Magnetic field generating means 2.102...Central magnet 21...Central magnetic pole 3...Outer circumferential annular magnet 31...Outer circumferential annular magnetic pole 103...Annular magnet 4... Inner circumferential annular magnet 41...First inner circumferential annular magnet 42...Second inner circumferential annular magnet 5.105...Yoke 10...Target application doujin TDT-K Co., Ltd. Patent attorney Yo Ishii

Claims (5)

[Claims] (1) In the step of forming a magnetic layer containing γ-Fe_2O_3 as a main component on a rigid substrate, a target containing Fe as a main component is placed in a vacuum chamber, a substrate is placed on the surface side of the target, and the target An outer annular magnetic pole is disposed facing the back surface, and an inner annular magnet magnetized in a direction substantially parallel to the target surface is placed inside the outer annular magnetic pole, and the outer annular magnetic pole side has the same polarity as the outer annular magnetic pole. A method for manufacturing a magnetic recording medium, characterized in that the vacuum chamber is filled with an inert gas containing O_2 gas and magnetron sputtering is performed to form a sputtered film on the substrate. (2) The method of manufacturing a magnetic recording medium according to claim 1, wherein magnetron sputtering is performed by arranging a central magnetic pole of opposite polarity to the outer annular magnetic pole inside the inner annular magnet. (3) The maximum value of the component of the magnetic flux density on the target surface in the direction parallel to the target surface is set to 200 to 400.
3. The method of manufacturing a magnetic recording medium according to claim 1, wherein magnetotron sputtering is performed while maintaining the G range. (4) The inside of the vacuum chamber is 4.0×10^-^4 Torr~
4. The method of manufacturing a magnetic recording medium according to claim 1, wherein magnetron sputtering is performed while maintaining the pressure at 2.0×10^-^3 Torr. (5) Power density PD per target
(Watt/cm^2) and O_2 gas flow rate OGF (SC
CM), the Fe_3O_4 film is formed by the magnetron sputtering, with the relationship between OGF=(3.7±0.8)PD−(3.9±0.7) and OGF>0. A method for manufacturing a magnetic recording medium according to any one of the above.